Sometimes Supreme Court cases are really about what’s between the lines.

The Supreme Courtis hearing arguments Monday challenging a federal agency’s power to regulate greenhouse gas emissions from big-industry polluters like power plants.

But as Roll Call’s David Hawkings explains, this case is less about the tug of war between environment and business and more about the balance of power between the legislative branch and the executive.

This is the third time in seven years the court has taken a look at the executive branch’s role in regulating climate change, as The New York Times notes in an editorial.

In 2007, the Supreme Court affirmed that the Environmental Protection Agency can expand the 1970s legislation known as the Clean Air Act to include regulating greenhouse gases. The law was written in a time when climate change wasn’t even acknowledged by scientists.

But some Republicans interpret the EPA’s attempts to do just that as another example of the president using federal agencies to bypass Congress.

The EPA’s regulation of power plants is “an intolerable invasion of Congress’s domain that threatens to obliterate the line dividing executive from legislative power,” reads a brief filed by 12 House Republicans submitted to the Supreme Court.

They also cite the president’s appointment of people to lead two federal agencies while Congress wasn’t really in session as an abuse of his power. (The Supreme Court heard arguments for that case in January.)

The battle lines weren’t always drawn this way — once upon a time, Congress actually wanted to curb greenhouse gas emissions.

Sen. John McCain, R-Ariz., ran for president in 2008 on a platform to tackle climate change that in part said “common sense dictates that the United States should take measured and reasonable steps today to reduce any impact on the environment.”

In 2009, the Democratic-controlled House passed a bill known as cap and trade, which mandated major cuts in businesses’ greenhouse gas emissions by putting a price on carbon dioxide.

But things stalled after that.

Cap-and-trade legislation never came up for a vote in the Senate, where Democratic leaders were worried about how it would play among moderates.